Portable cap spinning unit with hydraulic traverse



June 5, 1956 E. K. BAUER 2,749,055

I PORTABLE CAP SPINNING UNIT WITH HYDRAULIC TRAVERSE Filed Oct. 22, 19523 Sheets-Sheet 1 'JNVENTOR. ERA/6 T K. BAUf/P A TTORNEY.

E. K. BAUER Juhe s, 1956 PORTABLE CAP SPINNING UNIT WITH HYDRAULICTRAVERSE Filed 001. 22, 1952 3 Sheets-Sheet 2 ATTORNIYv June 5, 1956 E.K. BAUER PORTABLE CAP SPINNING UNIT WITH HYDRAULIC TRAVERSE Filed Oct.22, 1952 Sheets-Sheet 3 ll Hi INVENTOR.

ERNEST KVBAUER A TTORN Y.

United States Patent 1 Q PORTABLE CAP SPINNING UNIT WITH HYDRAULICTRAVERSE Ernest K. Bauer, Meadville, Pa., assignor to American ViscoseCorporation, Philadelphia, Pa., a corporation of Delaware ApplicationOctober 22, 1952, Serial No. 316,245 16 Claims. (Cl. 242-43.4)

This invention relates to winding'machines and more particularly to animproved traverse for such a machine which enables the production ofbetter and more desirable filament packages. I v

The present disclosure is directed to an improved winding machine asused in the textile industry for-winding yarn packages from strands orfilaments of a natural or synthetic fiber, but it will be understoodthat the nature of the filament used on the winding machine isimmaterial.

l have found that the most advantageous type of yarn package such ascustomarily wound on tubes or cones should have the followingcharacteristics. The tube should be substantially covered with yarnunder uniform tension. Tendency for sloughing of the yarn when unwoundshould be eliminated or reduced to a minimum. The center of gravity ofthe yarn package should be below the transverse centerline of the tube.To enable cleaning of the package, it is important that the entire outersurface of the yarn be stripped by removing a minimum number of layers,thus reducing waste. In order to achieve the above desirablecharacteristics in a yarn package, it is necessary to provide a traversemechanism for the winding machine that controls the layers of yarn woundon the tube to provide a special sequence, length, and relative locationof the layers. Complicated and expensive traverse mechanisms have beenheretofore designed for guiding the yarn onto the tube or cone. Thepresent device is characterized by its simplicity and ability to modifycompletely the type of yarn package wound with relatively minor changesor adjustments.

A primary object of the invention therefore is to pro vide an improvedtraverse mechanism for filament winding machines.

A further object of the invention is to provide a double cam traversemechanism for a yarn winding machine.

A further object of the invention is to provide a pair of cylindricalcams which, in conjunction with a pair of switches on the motor or flyerrail, control the points at which the rail reverses its traverse.

A further object of the invention is to provide means for temporarilyby-passing one of the limit switches on the traverse mechanism of a yarnwinding machine to permit limited over-travel of the motor rail therebyforming a tail.

Further objects will be apparent from the specification and drawings inwhich Figure l is a front View of a unitary winding machineincorporating the present invention, certain parts being sectioned;

Fig. 2 is a vertical section as seen at IIII of Fig. 1;

Fig. 3 is an enlarged sectional detail as seen at Ill-Ill of Fig. 1 withthe motor rail in a moved position;

Fig. 4 shows the wiring diagram of the present winding machine;

Fig. 5 is a schematic view showing partly in section the four-waysolenoid valve used to control the movement of the motor rail;

Fig. 6 is a diagrammatic view showing schematically the type of packagewound with allochiral cams of equal pitch;

2,749,055 Patented June 5, 1956 Fig.7 is a view similar to Fig. 6showing an entirelv difi'erent package formation using two identicalcams;

Fig. 8 is an enlarged detail of the cap and spindle in the position ofFig. 3 showing the manner of forming the tail;

Fig. 9 is an enlarged detail showing a pair of traverse cams of similartwist but of different pitch;

Fig. 10 is a diagrammatic representation of a yarn package partlysectioned as would be wound using the cams of Fig. 9.

Fig. 11 shows a pair of allochiral cams but of different pitch; and

Fig. 1.2 is a diagrammatic representation of a yarn package partlysectioned as would be found using the cams'of Fig. ll.

' The invention as applied to a cap yarn winding machine comprisesessentially the provision of a camshaft which is driven in timedrelation to the driving means for the spindle of the winding machine andwhich carries a pair of modified barrel cams. The motor rail has a pairof normally open limit switches which are closed at the end of eachtraverse in accordance with the angular position of the camshaft and camsurfaces. Generally, the cams are adjustable on the camshaft bothrotationally and axially. The cam surfaces are smooth helical edges but,of course, may be varied in accordance with the type of yarn packagethat may be desired. While the pitch of the cams surfaces may be thesame on each cam, I have found it desirable to use a higher pitch forthe bottom cam thus making the top of the yarn package more tapered thanthe bottom, and thereby providing a package having a relatively lowcenter of gravity.

When the cams are of the same right or left hand twist,

the layers of yarn wound on the tube or cone are gen erally of equallength and will be exactly equal in length if the cams have the samepitch. Since the camshaft is timed to make approximately two completerevolutions for winding each package, the yarn layers will be formed tooverlap each other at least twice at the points of maximum.displacement; each layer in a cycle being substantially the same lengthas the preceding layer but displaced axially. See Fig. 7. If the camsare allochiral (of opposite twist), the layers are shortened at each endso that there is no overlapping until the camshaft makes one completerevolution. See Fig. 6. I The motor rail is reciprocated by means of ahydraulic plunger which is, in turn, controlled by a solenoid-actuatedhydraulic valve. The solenoids areenergized by switches mounted on themotor rail which contact the cam edges. The cap can be moved axially bymeans of suitable linkage, and when the cap is so displaced, anadditional switch in series with the upper limit switch is held. open bythe linkage to prevent energization of one of the valve solenoids thusforming a tail for attachment to another package.

Referring to Figs. 1 and 2, l have shown my present improved traversemechanism applied to a more or less conventional cap yarn windingmachine. It will be understood however, that the improved traverse isuseful in any type of yarn winding machine as well as coil Winders wherethe shape of the coil or yarn package should be carefully controlled.The spindle motor 15 which drives a tube 16 through the conventionaltube holder 17 and tube drive assembly 18 is mounted on the motor rail19. Rail 19 is, in turn, carried by a bracket 20 slidable in ways 21 onvertical frame member 22.

In accordance with conventional construction of windving machines, a cap23 is supported on a cap rod 24 3 28. The rod 24 extends through thehollow shaft of motor and does not rotate. It may be moved axially,however, by means of a treadle 30. The frame member 22 is secured in themain frame assembly 31 at the top, and to cross member 32 at the bottom.A second cross member 33 mounts bracket 27 as well as bracket 34 onwhich the treadle is pivoted. A link 35 pivotally connects treadle 30and yoke 36 which is secured to the bushing 26 and to the cap rod 24 sothat they move in unison when the treadle is pressed against the actionof spring 28. I

The motor rail 19 together with tube 16 are moved vertically up and downthrough the action of a hydraulic cylinder 37 secured to cross members32 and 33 and carrying a piston and rod assembly 38 bolted to bracket20. A shield or guard 39 is provided over the bottom 'of cylinder 37 toenclose the tail rod 38a when in its bottom position. Fluid foractivating the piston in the cylinder is controlled and regulated bymeans of a fluid valve 40 (Fig. 5) having an upper fluid connection orconduit 41 between the valve and cylinder 37, and a lower similarconduit 42. Air chambers 43 and 44 are connected to conduits 41 and 42respectively to provide smooth action of the piston 38 in cylinder 37.Air chambers 43 and 44 are desirably provided with valves 45 and 46respectively connected to lines 41 and 42.

Fluid for actuating the motor rail assembly is delivered to valve 40through conduit 50 from pump 52 which is, in turn, driven by motor 53.The pump and motor are mounted on the subframe assembly 54 which iscarried by frame members 55 and 56.

Activation of valve assembly 40 is achieved through solenoids 58 and 59which reciprocate a piston valve elc ment 60 to alternately connect thedischarge conduit 50 from pump 52 to conduits 41 and'42. The position ofthe valve 60 shown in Fig. 5 introduces fluid under pressure throughconduit 41 to the top of cylinder 37. Fluid that had been in thecylinder is vented through conduits 42 and 51. When solenoid 58 isenergized and solenoid 59 de-energized, the valve element 60 shifts inthe valve housing to connect-pressure conduit 50 and cylinder conduit 42and simultaneously permitting fluid from the cylinder to dischargethrough conduit 41. into conduit 51.

The solenoids 58 and 59 are selectively energized to operate the valve40 by means of switches 61 and 62 mounted on the motor rail 19. Theswitches have rollers 61a and 62a respectively which contact the camsurfaces 65 and 66 on cylindrical cams67 and 68 respectively. These camsare adjustably secured to a camshaft 69 by means of collars 7 0, 70 andset screws 71, 71. Camshaft 69 is journaled at its upper end in abracket and at its lower end carries a worm wheel 76 driven by a meshingworm gear 77 carried on shaft78. Motor 79 drives camshaft 69 throughreduction gearbox 80, sprockets 81. 82, and chain 83. The speed of shaft69 is such that it turns approximately two revolutions during thecomplete winding of a package. A guard encloses earns 67 and 68, and isslotted at 86 to permit access of rollers 61a and 62a to the camsurfaces 65 and 66.

Fig. 4 shows the wiring diagram in which motor 53 is connected to asource of electrical current 87 through a suitable switch 88, and themotor 79 is connected to two sides of the same source of current througha transformer 89 and switch 90. Solenoids 58 and 59 are likewiseconnected to the low tension side of transformer 89 through leads 91 and92.

In operation, switches 88 and are closed thus starting both motors 53and 79. The motor rail 19 then moves either up or down depending uponthe position of valve element 60 in valve assembly 40. However, therecipro cation of the motor rail will be stopped at the position shownin Fig. 3 when the operator depresses treadle 30. This not only lowerscap 23 to the dottedline position shown in Fig. 8 but also opens aswitch 93 in the circuit to solenoid 59 so that this solenoid will notbe energized to lower the motor rail until the operator releases treadle30. In winding tubes with yarn, it is desirable to pro vide a tail 94for each yarn package so that the tail can be tied to the leading end ofthe next yarn package thus avoiding any interruption in the unwinding ofa plurality of packages. A bracket 95 secured to treadle 30 operatesswitch 93 in accordance with the position of the treadle, and the axialdisplacement or lowering of cap 23 may be regulated by means of a setscrew 96 at the end of the treadle.

In the customary manner, yarn feeds through an eye or pig tail 97mounted on top of the frame by means of a bracket 98 so that a balloonis formed by the yarn strand 99 as it revolves around the cap 23 at highspeed. After the tail 94 has been sufficiently wound, the operatorreleases treadle 30 which, in turn, closes switch 93 and permits thetraverse mechanism to commence normal operation. The motor railreciprocates up and down to wind layers of yarn or filament on tube 16and the reversing of the motor rail travel is controlled by limitswitches 61 and 62 and cam surfaces 65 and 66. The upper limit of eachyarn layer is determined by bottom switch 62 and bottom cam 66, whereasthe lower limit of each yarn layer is determined by upper switch 61 andupper cam surface 65. The switches 61 and 62 are normally open so thatwhen they are closed respectively, solenoids 58 and 59 are energized tomove valve 60 as explained above. It will therefore be understood thatthe length of each yarn layer as well as its axial positionon tube 16 iscontrolled by the axial position of cam surfaces 65 and 66 which arecontacted by the switches 61 and 62.

Referring to Figs. 6 and 7, the various shapes of yarn package that canbe achieved with the same or slightly modified cams will be explained.Fig. 6 shows earns 67 and 68 diagrammaticallyand these two cams are ofequal pitch and allochiral with the high parts of each cam in axialalignment. These cams provide an initial maximum traverse whichisgradually shortened equally at each end by each cam as the camshaft 69turns. The shape of a yarn package formed with such cams is also showndiagrammatically in "Fig. 6 in which the first yarn layer covers themaximum length of the tube 16. The second layer is shortened both at thetopand the bottom until the shortest layer is wound. This builds asymmetrical wrapping which is tapered both at thetop and the bottom.When the camshaft 69 makes one complete turn, the abovewrappingisrepeated so that the first layer after the cams have made oneturn extends substantially to the firstlayer on the tube. This is due tothe fact that this first maximum repeat layer is wound directly over thepreceding shortest layer due to the abrupt slope of the cam surface. Asthe package continues to build, the layers are similarly shortened ateach end so that a yarn package having a short outer layer andsymmetrical tapering conical ends is provided. Such a yarn package givesgood tube coverage, fair tension and minimum sloughing tendency. Thepackage cannot be completely cleaned, howevenexcept by removing nearlyhalf of the yarn wound thereon. Since earns 67 and 68 are exactlyallochiral, the yarnpackage is symmetrical with respect to thetransverse centerline of the tube.

Fig. 7 illustrates a variation in the yarn package'form whichmay beachieved by using a second cam 67a in place of cam 68. In this case,earns 67 and 6711 are identical to each-other. The high pointof each camis axially aligned 'oncarnshaft 69 with the result that the travel ofthe motor rail is always the same but it gradually shifts orprogressesfrom one end of the .tube to the other. 'A' yarn package wound with-cams67 and 67a is shown diagrammatically in Fig. 7 and it will be noted thateach-layer is intermediate in length. to the maximum and minimum layersshown in Fig. 6. However the first layer starts at the bottom of tube 16and is carried .up

comparison.

gasses .wardly to a point substantially above the 'centerline of thetube. The second layer is of the same length as the first layer but isdisplaced upwardly therefrom a slight amount in accordance with thepitch of the cams. In this way the layers are progressively wound on topof each other until the last layer of the first revolution of thecamshaft. This layer extends from the maximum top position on tube 16 toa point somewhat below the transverse centerline of the tube andsymmetrically opposite with respect thereto as compared to the firstlayer. When camshaft 69 has gone just beyond one turn, the windingshifts axially and abruptly to form a downward layer extending from themaximum bottom position to the same point where the first layer ended.The cycle is thus repeated during the second revolution of the camshaftand the resulting package is almost identical in outer appearance to thepackage wound in Fig. 6. However, it will have several noticeably betterfeatures. In the package of Fig. 7 the tube is covered, the tension isfairly uniform, and the sloughing tendency is reduced to a minimum.Furthermore, it is possible to clean approximately 70% of the packagesurface by removing only the outer yarn layer. This, of course, is adecided advantage over the package shown in Fig. 6.

Further improvements in the package that can be wound with the presentinvention are shown in Figs. and 12 and these advantages can be achievedby using cams similar to those shown in Figs. 6 and 7 but with slightlydifferent pitch. The upper cam 67 has been retained throughout thevarious modifications as a basis of However, in Fig. 9 the lower cam 100is of the same slope or twist as cam 67 but it has a greater pitch.Since cam 10%) controls the shape of the upper part of the yarn package,the greater pitch provides more slope in the top conical portion 161than is formed in the lower conical portion .102. This lower center ofgravity of the package insures smooth running at higher unwindingspeeds, and it reduces sloughing tendency because the yarn strand whenunwound is drawn from or over the more gradually tapering end of thepackage.

in Fig. 10 the layers are wound on the tube 16 in a manner generallysimilar to that shown in Fig. 7. Due to the fact that the pitch of thecams is not equal, there will be a gradual increase or decrease in thelength of each layer. This increment or decrement as the case may be is,however, far less than in the package of Fig. 6. With cams 67 and 100,it will be seen that the minimum layer length occurs when the switchrollers 61a and 62a contact points 163 and 104 on the cams. The width ofthe layers then gradualy increases to a maximum until the rollerscontact points 105 and 106 on the cams. This difference in the length ofeach layer may, of course, be controlled as desired by the relativeshape or pitch that is used.

Fig. 11 shows upper cam 67 used in conjunction with cam 110 which isallochiral to cam 67 and has a greater pitch similar to cam 100. Thiscombination of cams winds a yarn package shown diagrammatically in Fig.12 which is similar to the package of Fig. 6 in that the first layer ofyarn wound on the tube is of maximum length and subsequent layersgradually decrease in length. The decrement, however at each end of thelayer is unequal. Since the pitch of earn 110 is greater than the pitchof cam 67, the shortening of the layers takes place more rapidlyat thetop 111 of the package than at the bottom 112. Therefore, a package ofthe same general shape as that shown in Fig. 10 will be wound after tworevolutions of camshaft 69. The characteristics of the package of Fig.12 with regard to cleaning approximate those of the Fig.6 package.However, sloughing is reduced and higher speeds are possible because ofthe more gradual taper at the top of the package.

In addition to the unexpected differences in package construction thatcan be achieved by using two cams of p the type disclosed herein whichhave helical surfaces con-" trolling the length of each yarn layer as itis progressively wound, further variations are possible by changing theaxial and rotational relationship of the cam surfaces simply byloosening either or both set screws 71, 71 and positioning the cams onshaft 69 as may be desired. The examples given above are illustrative ofonly a few of the wide variations possible. However, it has been foundthat the construction shown in Fig. 9 which winds the yarn package ofFig. 10 gives what is considered to be the best all around yarn package.This package has low center of gravity and more gradual tapering at thetop which reduces or eliminates sloughing and the package can be cleanedin a maximum area by removing and therefore wasting the minimum amountof yarn. The relative importance of one or more of these advantages willdepend upon circumstances, but with the present invention, it is readilypossible to provide the exact type of package giving the particularadvantage that is desired with a minimum expense and alteration of thetraverse mechanism. The yarn packages described herein have all beenformed with two complete revolutions of the camshaft 6?. it will beunderstood, however, that one or more than two revolutions can be used.Nevertheless, in all traverses in which the rail reverses more yarn iswound at the point of reversal because there is never instantaneouschange of direction. If the reversals are on top of each other or tooclose together, a lump of yarn will be formed thereby inducingsloughing. By repeating the cycle at least twice per package, theconsecutive reversals causing lumping are suificiently far apart thatthere is no appreciable build up.

it will be appreciated that the illustrations of the yarn packages arediagrammatic only and the thickness of each layer has been greatlyenlarged in order to bring out the nature of the winding. Furthermore,the provision of the tail shown in Fig. 8 which is readily provided withthe present invention has been omitted from the showings of Figs. 6 and7 in the interest of clarity.

It must be understood that I have provided a simple and inexpensivetraverse mechanism that is capable of producing a coil or yarn packageselectively having the best combination of all features desired andwhich can be appiied to any type of filament winding machine.

I claim:

1. A traverse assembly for winding machines comprising a filamentguiding member, a filament receiving member said members being mountedreciprocably and rotatably with respect to each other, a shaft mountedin spaced relation to the axis of rotation of one of said members andfixed against axial movement in a direction parallel thereto, means forturning said shaft at a predetermined relative constant speed withrespect to the rotation and reciprocation of said members, a pair ofoppositely facing cam surfaces carried by said shaft, electrical contactresponsive means on the reciprocable member for contacting each of saidcam surfaces during reciprocation, and means responsive to activation ofsaid electrical contact means for reversing the direction of travel. ofthe reciprocable member.

2. A traverse assembly for winding machines comprising a filamentguiding member, a filament receiving member said members being mountedreciprocably and rotatably with respect to each other, a shaft mountedin spaced relation to the axis of rotation of one of said members andfixed against axial movement in a direction parallel thereto, means forturning said shaft at a predetermined relative speed with respect to therotation and reciprocation of said members, a pair of barrel cam-s eachhaving an oppositely facing cam surface carried by said shaft,

means on the reciprocal member for contacting the cam surface on each ofsaid cams during reciprocation, and hydraulic means responsive toactivation of said contacting means for reversing the direction oftravel of the reciprocable member.

3. A traverse assembly for winding machines comprising a filamentguiding member, a filament receivingmemher said members being mountedreciprocably and rotatably with respect toeach other, a shaft'mounted inspaced relation to the axis of rotation of one of said members and fixedagainst axial movement in a direction parallel thereto, means forturning said shaft at a predetermined relative speed with respect to therotation and reciprocation of said members, a pair of identical barrelcams each having an oppositely facing cam surface carried by said shaft,means on the reciprocable member for contacting the cam surface on eachof said cams during reciprocation, and means responsive to activation ofsaid contacting means for reversing the direction of travel of thereciprocable member.

4. A traverse assembly for winding machines comprising a filamentguiding member, a filament receiving memher said members being mountedreciprocably and rotatably with respect to each other, a shaft mountedin spaced relation to the axis of rotation of one of said members andfixed against axial movement in a direction parallel thereto, means forturning said shaft at a predetermined relative speed with respect to therotation and reciprocation of said members, a pair of allochiral barrelcams each having an oppositely facing cam surface, means on thereciprocable member for contacting the cam surface on each of said camsduring reciprocation, and means responsive to activation of saidcontacting means for revers ing the direction of travel of thereciprocable member.

5. A traverse assembly for winding machines comprising a filamentguiding member, a filament receiving member said members being mountedreciprocably and rotatably with respectto each other, a shaft mounted inspaced relation to the axis of rotation of one of said members and fixedagainst axial movement in a direction parallel thereto, means forturning said shaft at a predetermined relative speed with respect to therotation and reciprocation of said members, a pair of barrel cams havingthe same twist and unequal pitch on oppositely facing cam surfaces ofeach cam, means on the reciprocable member for contacting the camsurface on each of said cams during reciprocation, and means responsiveto activation of said contacting means for reversing the direction oftravel of the reciprocable member.

6. A traverse assembly for winding machines comprising a filamentguiding member, a filament receiving memher said members being mountedreciprocably and rotatably \vitlrrespect to each other, a shaft mountedin spaced relation to the axis of rotation of one of said members andfixed against axial movement in a direction parallel thereto, means forturning said shaft at a predetermined relative speed with respect to therotation and reciprocation of said members, a pair of barrel cams havingopposite twist and unequalpitch, means on the reciprocablemember-for-contacting the cam surface on each of said cams duringreciprocation, and means responsive to activation of said contactingmeans-for reversing the direction-of travel of the reciprocable member.

7. A traverse assembly for winding machines comprising a filamentguidingmember, a filament receiving member said members being mountedreciprocably and rotatablywith respect to each other, a shaft mounted inspaced relation to the axis of rotation of one of said members, meansfor turning said shaft at a predetermined relative speed with respect tothe rotation and reciprocation of said members, a pair of oppositelyfacing cam surfaces carried bysaid shaft, meanson the reciprocablemember for contacting the cam surface on each of said camsduringreciprocation, means responsive to activation of said contactingmeans for reversing the direction of travel of the reciprocable member,and means for axially displacing the filament receiving member withrespect to the filament guiding member beyond the normaLcam controlledlimit to form a tail.

8. A traverse assembly for winding machines comprising a filamentguiding member, a filament receiving member said members being mounted,reciprocably and rotatably with respect to each other, ashaft mountedin spaced relation to the axis of rotation of one of said members,meansfor turning said shaft at a predetermined relative speed withrespect to .the rotation and reciprocation of said members, a pair ofoppositely facing cam surfaces carried by said shaft, means on thereciprocable member for contacting the cam surface on each of said camsduring reciprocation, means responsive to activation of said contactingmeans for reversing the direction of travel of the reciprocable member,and means for rendering the reversing means inoperative to provide atail.

9. A traverse assembly for winding machines comprising ,a filamentguiding member, a filament receiving member, said members being mountedreciprocably and rotatably with respect toeach other, a camshaft mountedin spaced relation to the axis of rotation of one of said members andfixedagainst axial movement in a direction parallel to the axis thereof,means for turning said camshaft at a predetermined relative speed withrespect to the .rotation and reciprocation of said members, a firstbarrel shaped cam having a spiral cam surface mounted on said camshaft,a second barrel shaped cam having an oppositely facing spiral camsurface mounted on said camshaft, apair of limit switches mounted on there ciprocable member and positioned to engage the cam surfaces, meansfor reciprocating the reciprocable mem ber, means for reversing thedirectionof travel of said last named means, and means for energizingsaid reversing means upon respective closing of the limit switches .bythe cam surfaces.

10. Apparatusas defined in claim 9 in which the cams are identical.

11. Apparatus as defined in claim 9 in which the cams are allochiral.

12. Apparatus as defined in claim 9 in which the cams have the sametwist and are of unequal pitch.

13. Apparatus as defined in claim 9 in which the cams are of oppositetwistand have unequal pitch.

14. Apparatus as defined in claim 9 having a manually operable switch inseries with one of the limit switches for selectively rendering thereversing means inoperative to provide limited over-travel of thereciprocable member.

15. Apparatus as defined in claim 14.having means for simultaneouslyopening the switch and moving the reciprocable member with respect tothe rotatable member.

'16. A .traverse assembly for winding machines comprising a shaft, meansfor rotating said shaft, a pair of spiral cam surfaces connected to androtatable with said shaft, a reciprocable filament layer forming memberassociated with said shaft, means for reciprocating said layer formingmember, and means carried by the reciprocable member for reversing saidreciprocating means upon contact with said cam surfaces, saidlastmentioned means comprising a pair of limit switches positioned to.contact the cam surfacesand means for rendering one of said limitswitches inoperative to permit limited over- .travel of the layerforming member beyond its normal reversing position.

References Cited in the file of this patent UNITED STATES PATENTS2,254,220 Hubbard Sept. 2, 1941 2,461,855 Tornberg Feb. 15, 19492,513,815 Nelson July 4, 1950 2,539,267 Nildes Jan. 23, 1951 2,575,031Smith Nov. 13, 1951 2,5973537 Sigmon May 20, 1952 FOREIGN PATENTS505,200 Belgium Aug.31, 1951

